NMMNG says not to seek external validation. Is working on raising our SMV not doing just that?

The key is that NMMNG is talking about validation as an unhealthy, needy emotional drive to get your sense of self-worth from others. If you feel like a loser unless you get complements on your clothes, if you feel ashamed of your body unless people ask if you've started lifting, etc.

Simple approval, on the other hand, isn't necessarily tied to your intrinsic sense of self worth. Getting someone to buy into your business plan or agree that you have qualifications for your job is a necessary part of a career, but it's a simple, practical demonstration of value. Smiling a little when some chick in a bar rubs your biceps but knowing that you are the shit already regardless of if that happens or not. These "validations" are just ordinary things now, rather than being an emotional need that you'll twist your relationships inside out to manipulate people into giving you so you can fill that craving hole in your soul left by <insert sob story here> .

With NMMNG as you note, it's possible to try to raise your self esteem and accept yourself exactly as you are - that's one route. With MRP advice to raise your SMV, you're simultaneously improving yourself and trying to remove the unhealthy craving - this is another entirely compatible other route. Two ways to the same end. You're trying to boost your self confidence and sense of intrinsic value by doing the recommended SMV boosting things like dressing better. And when you feel better about yourself just because you acknowledge that you're quite the catch, that craving need for validation from others to acknowledge your you nice new wardrobe starts to dry up.